Salmonella typhimurium tester strain TA100 is being used in a study of the reaction rates of styrene oxide optical isomers. Previous studies have shown that enantiomers (optical isomers) of some compounds differ in their production of mutation, carcinogenicity, or their interactions with activating or detoxifying enzymes. This study has shown that styrene oxide, a compound with industrial significance, has optical isomers which differ in their mutagenicity levels while maintaining similar rates of mutation production. Studies will be continued using reconstituted enzyme systems in order to determine if this difference exists where conjugation with glutathione is followed using mutation as the endpoint. Testing of styrene oxide conjugates; styrene glycol, styrene-glutathione, styrene-cysteinyl-glycine, styrene-cysteine and styrene-mercapturic acid showed no mutagenic or toxic responses in the absence of S9 activation.